Magnetic tape cassette

ABSTRACT

A magnetic tape cassette in which critical parts subject to wear are coated with a hard coating such as an ultraviolet-cured resin. Among other effects, the generation of rubbed-off powder is reduced, thereby reducing the amount of data drop-out. Also, the case of the cassette is protected from damage.

This is a divisional of application Ser. No. 07/889,434 filed May 28,1992, now U.S. Pat. No. 5,219,074 which is a divisional of applicationSer. No. 07/799,204 filed Nov. 27, 1991 now U.S. Pat. No. 5,175,661,which is a divisional of application Ser. No. 07/697,560 filed May 9,1991, now U.S. Pat. No. 5,101,307, which is a divisional of applicationSer. No. 07/323,926 filed Mar. 15, 1989, now U.S. Pat. No. 5,041,938.

BACKGROUND OF THE INVENTION

The present invention related to a magnetic tape cassette, and moreparticularly to a magnetic tape cassette suited for use in a digitalaudio tape recorder (DAT).

Recently, cassette tape recorders have become very compact in size andlightweight, and magnetic tape cassettes of a compact size for such taperecorders have now been extensively used. In the field of audioequipment, the above-mentioned DAT has been developed (see, for example,ELECTRONICS, June 1987, pages 65-70), and this has enabled longrecording and playback times of high quality and high density.

Magnetic tape cassettes, which are capable of recording and playbackover a relatively wide frequency band as is the case with conventionalvideo tape cassettes, have been developed for use in DATs. With respectto the appearance and configuration of such magnetic tape cassettes fora DAT, they are more compact in size and handier to carry thanconventional audio compact cassettes.

As a result, magnetic tape cassettes for DATs tend to be carried aroundand used outdoors as frequently as or more frequently than conventionalaudio compact cassettes.

As is well known, in a DAT analog signals are converted into digitalsignals to effect recording. Therefore, if the magnetic tape has aminute flaw or dust is lodged thereon, signal dropout can occur. Toreduce the chances of this occurring, such magnetic tape cassettes aregenerally provided with a special dust prevention mechanism.

In one example of such a special dust prevention mechanism, there areprovided at the bottom of the cassette a slider and a lock mechanism forthe slider. When the magnetic tape cassette is placed in use, the slideris moved in sliding contact with the bottom surface of the cassette halfto open the lower side of an opening provided at the front side of thecassette to expose the magnetic tape so that the magnetic tape can bepulled out from the cassette and placed in contact with a magnetic head.When the magnetic tape cassette is not in use, the slider is returned,in sliding contact with the bottom surface of the cassette, to retractthe magnetic tape into the cassette, that is, to its sealed condition,thus closing the lower side of the opening.

Generally, the cassette case composed of two cassette halves is made ofan ABS resin and a polystyrene (PS) resin, and in most cases the slideris made of a polyoxymethylene (POM) resin. POM resin is harder thanacrylonitrile butadiene styrene (ABS) resin and PS resin, and thereforeif the slider is reciprocally moved repeatedly as described above over aprolonged period of time, the bottom surface of the cassette half tendsto wear due to friction between the two components.

The rubbed-off powder produced as a result of this action adheres to themagnetic tape at the point where it runs on the slider, resulting insignal dropout.

In view of the above, it has conventionally been proposed to provideprojections or stepped sections on the contacting surface between thecassette half and the slider to decrease the area of contact between thetwo in an attempt to reduce the production of such powder. With thisarrangement, however, satisfactory results could not be obtained. Thus,it has been desired to provide an arrangement by which high-levelrecording and playback with high density recording can be maintainedover a prolonged period of time.

The invention further relates to a magnetic tape cassette in which amagnetic tape wound around a pair of hubs is supported within a cassettecase so that the magnetic tape can be run to effect recording andplayback.

In video equipment, such as a video tape recorder or an audio taperecorder, there have been extensively used magnetic tape cassettes inwhich a magnetic tape wound around a pair of hubs is supported within acassette case in such a manner that the magnetic tape can be run toeffect recording and playback. Such a magnetic tape cassette when in useis loaded into a cassette loading portion of a recording and playbackdevice, that is, a video tape recorder or an audio tape recorder. Sincethe magnetic tape must be disposed in proper contact with the magnetichead of the recording and playback device, it is necessary to accuratelyposition the cassette case with respect to the cassette loading portionwhen the former is loaded in position into the latter.

A positioning method used, for example, with an audio magnetic tapecassette 220 will now be described with reference to FIG. 1. A cassetteloading portion 205 defined by a recessed portion of a tape recorderbody 201 is covered by a bucket 202 pivotally movable to one endthereof. Mounted on a chassis 206 of the cassette loading portion 205are a pair of reel shafts 209 which are inserted in respective reelshaft insertion holes 223 of the magnetic tape cassette 220 when thecassette is loaded. Capstan 208 is also mounted on the chassis 206 andcooperates with a pinch roller 211 disposed in opposed relation theretoso as to hold the magnetic tape 224 therebetween to run the same at aconstant speed. The pinch roller 211, a recording and playback head 212,and an erasing head 213 are linearly arranged on a movable chassis 210,and these components are introduced into openings 225 and 226 formed inthe front end of the loaded magnetic tape cassette 220 when the movablechassis 210 is driven in the direction of an arrow A for effecting arecording and playback.

Two metal positioning pins 207a and 207b are fixedly mounted on thechassis 206 near the recording and playback head 212, the pins 207a and207b extending in the direction of thickness of the loaded cassette.

The magnetic tape cassette 220 has positioning holes 221 and 221bdisposed near the opening 225 which open in the direction of thicknessof the cassette, the positioning pins 207a and 207b being adapted to beinserted into the positioning holes 221a and 221b, respectively. Themagnetic tape cassette also has capstan insertion holes 222 formed nearthe openings 226 and opening in the direction of thickness of thecassette, the capstan 208 being loosely fitted in the capstan insertionhole 222.

Through a manual or an automatic operation, the magnetic tape cassette220 held by the bucket 202 is angularly moved into the cassette loadingportion 205 defined by the recess. At this time, the positioning pins207a and 207b are slidingly inserted into their mating positioning holes221a and 221b, respectively, and-the capstan 208 is loosely fitted inthe mating capstan insertion hole 222.

Therefore, the inner peripheral surfaces of the positioning holes 221aand 221b are rubbed by the positioning pins 207a and 207b, respectively,each time the magnetic tape cassette 220 is loaded and unloaded.

As explained above, the cassette case of the magnetic tape cassette 220is generally molded of a resin such as an ABS resin or a PS resinbecause of its processability and low cost. Therefore, when the cassettecase is subjected to repeated rubbing action as encountered with theinner peripheral surfaces of the positioning holes 221a and 221b, thecassette case is gradually worn because these resins are inferior inwear resistance.

As a result, the positioning holes 221a and 221b become deformed, andhence the magnetic tape cassette fails to be accurately loaded inposition into the cassette loading portion, thereby adversely affectingthe proper positional relation between the magnetic head and thecassette. This causes various tape running problems such as impropercontact between the tape and the magnetic head, which results in anunstable reproduction output, and signal dropout due to the adhering tothe magnetic tape 24 of powder produced as a result of the above rubbingaction.

Further, a magnetic tape cassette for use in audio equipment, whenstored, is usually contained in a magnetic tape cassette storage casemade of a plastics material.

The magnetic tape cassette has openings for receiving a magnetic head,etc., of a recording and playback device, and the magnetic tape extendsacross these openings. The storage case prevents dust from entering thecassette during storage, protects those portions of the magnetic tapedisposed in the above openings, and protects the whole of the cassette.

There are various known shapes and constructions of storage cases.Generally, the storage case has a lid having a pocket for holding thecassette, and a casing having a pair of rotation preventing lugs forinsertion into respective shaft insertion holes of the magnetic tapecassette.

Pivot pins formed respectively on right and left side walls of thecasing are fitted in respective holes formed through right and left sidewalls of the lid so that the lid and the casing can be opened and closedrelative to each other similar to a door.

Further, the casing has retainer projections, and the lid has engagingholes with which the retainer projections are engaged when the lid isclosed relative to the casing, thereby holding the lid againstaccidental opening movement.

In view of the manufacturing cost, the casing and the lid are generallymade of an acrylonitrile styrene (AS) resin, PS resin, polypropylene(PP) resin or the like.

The storage case is opened and closed each time the magnetic tapecassette is placed in storage and removed therefrom. Storage cases quiteoften rub together during times when they are stored and carried. Whenthe storage case is opened and closed, the pivot pins are angularlymoved within their respective mating holes, and the pivot pin and theperipheral surface of the hole rub together, producing rubbed-offpowder. With respect to the retainer projections and the engaging holes,a similar rubbing action occurs to further produce rubbed-off powder.Such rubbed-off powder is a fine powder and therefore is liable to bedispersed within the storage case to adhere to the surface of themagnetic tape exposed through the above-mentioned openings. As a result,recording and playback cannot be effected at those portions of themagnetic tape to which the rubbed-off powder adheres as signal dropoutoccurs. In the event of such signal dropout, as described in TELEVISIONTECHNOLOGY, (September 1985, page 34, a Japanese journal published byDenshi Gijutsu Shuppan K. K.) picture flicking occurs and the reproducedaudio is noisy.

Thus, despite the fact that the storage case of a conventional designwas originally intended to protect the magnetic tape cassette and toprovide dust prevention, rubbed-off powder can still be produced overlong periods of time.

The above-mentioned AS, PS and PP resins have a low surface hardness(strength), and therefore when the storage cases rub together duringstorage and carrying, the surface thereof is susceptible to damage. Anindex card indicative of the contents of the recorded information isoften contained within the storage case. If there are scratches on thecase surface, the index card and an index bonded to the cassette surfacecan be obscured. Such a phenomenon is also undesirable from theviewpoint of appearance. Thus, these problems have made it quitedifficult to use a storage case for a long period of time.

In view of the above, it has been proposed to provide ribs on marginalportions of the outer surface of the storage case so that the outersurfaces of the storage cases do not contact each other. However, thishas been found not sufficient for the prevention of scratching. On thecontrary, providing ribs reduces the area of contact between theadjacent storage cases, and therefore they are liable to slide withrespect to each other. As a result, the incidence of accidental droppingand damage is increased.

Also, in magnetic tape cassettes, the magnetic tape wound on the pair oftape winding bodies is rotatably mounted within a cassette case composedof upper and lower cassette halves, each of a one-piece moldedconstruction made of a synthetic resin.

One particular tape winding body used in a video tape cassette has upperand lower flanges formed respectively on upper and lower ends of thetape reel to prevent the lateral edges of the magnetic tape fromcontacting the inner surfaces of the cassette halves and also toregulate the position of winding of the tape so as to maintain even tapewinding. A tape winding body of another type, such as one used in anaudio tape cassette, has a pair of upper and lower friction sheets eachmounted between the end face of the hub and the inner surface of thecassette half to reduce the amount of friction between the lateral edgeof the magnetic tape and the inner surface of the cassette half tothereby stabilize the running of the magnetic tape and also to maintaineven tape winding.

Each of the hubs is rotatably supported by respective cylindrical spoolsupport walls formed on the upper and lower cassette halves in such amanner that the hub is prevented from moving in the horizontal directionwith respect to the cassette. As a result, however, the upper and lowerportions of the inner periphery of the hub are always rubbed by thecorresponding spool support walls.

The flanged tape reel has a projection formed at an upper surfacethereof and disposed at its axis. A metal plate mounted on the uppercassette half urges this projection inwardly of the cassette so as tolimit the vertical movement of the tape reel. Further, the outerperipheral edges of the flanges of the tape reel contact the side wallsof the cassette halves to limit the horizontal movement of the tapereel.

Therefore, due to vibration and shock occurring, for example, duringtransportation of the cassette, the outer peripheral edges of theflanges of the flanged tape reel are rubbed by the above side walls, andthe outer surface of the lower flange is rubbed by the inner surface ofthe lower cassette half.

As already discussed, cassette cases have recently been molded of ageneral-purpose resin of inferior wear resistance such as ABS and PSresin because of its processability and reduced manufacturing cost. Onthe other hand, the tape winding bodies such as the above-mentioned huband flanged tape reel are generally molded of a resin of high wearresistance such as a polyoxymethylene resin. Therefore, the cassettecase is gradually worn.

As a result, the spool support walls are deformed, and hence the axis ofrotation of the tape reel can deviate during rotation, which results inunstable running of the magnetic tape. Further, the rubbed-off powderresulting from this action adheres to the magnetic tape, causing varioustape troubles such as signal dropout.

Yet further, the invention relates to a magnetic tape cassetteincorporating a pad for stabilizing the running of a magnetic tape.

Magnetic tape cassettes for audio and video use are provided with guidemembers such as an immovable tape guide in sliding contact with themagnetic tape and a guide roller rotatably engaged with the magnetictape to guide the running of the tape. These guide members are arrangedto contact with either the backside (the base side) or the front side(the magnetic layer side) of the magnetic tape. Particularly, therotatable guide roller is used mainly because it can avoid unnecessaryfrictional sliding contact with the magnetic tape. Particularly,recently high-density magnetic tapes have been used, and therefore sucha rotatable guide roller has been increasingly used to avoid signaldropout caused by scuffing of the magnetic tape as a result of directsliding contact of the magnetic tape and an immovable tape guide.

Such guide rollers are of a cylindrical shape, and some have a flange attheir lower end. Generally, the guide roller is made of a plasticsmaterial having a relatively high wear resistance, such as POM resin.The magnetic tape is in sliding contact with the outer periphery of theguide roller, that is, the tape extends around the guide roller througha certain angle, and therefore the guide roller considerably influencesthe running of the magnetic tape. There are occasions when slippageoccurs between the magnetic tape and the reels around which the tape iswound when the tape is stopped subsequent to a fast-forwarding operationto thereby displace the magnetic tape out of position. As a result, themagnetic tape can accidentally project from the tape extraction openingof the cassette, subjecting it to damage. This tendency is particularlymarked in cassettes incorporating a rotatable roller.

To avoid such problems, a pad is provided within the cassette for urgingthe magnetic tape against the tape guide or the rotatable roller.

For example, such a pad may be molded of a plastics material, and beresilient, short and thin. The pad is fixedly secured at one end andurged into a curved configuration to have an elastic force so that thepad urges the magnetic tape against the guide roller.

Generally, the pad has a plate-like base molded of polyethyleneterephthalate (PET) resin and a layer of ultra-high-molecular-weightpolyethylene or Teflon formed on the base. Polyethylene terephthalateresin has the drawback that it is inferior in wear resistance.Ultra-high-molecular-weight polyethylene and Teflon though are expensivematerials and therefore the pad has generally been costly because of itsmaterial cost and processing cost.

To reduce the cost, it has been proposed to provide a one-piece moldedplate made solely of ultra-high-molecular-weight polyethylene. Althoughsuch a pad is superior in wear resistance with respect to slidingcontact with the magnetic tape, it is inferior in resistance to creep.Therefore, there have been encountered problems such as an unstableurging force applied to the magnetic tape.

The invention yet further relates to a magnetic tape cassette having atransparent window provided in cassette case body.

The shape and appearance of audio and video magnetic tape cassettes varydepending on their use. Despite this, magnetic tape cassettes have acommon feature in that they are usually provided with a transparentwindow for viewing the interior of the magnetic tape cassette.

The transparent window is very useful for observing the windingcondition of the magnetic tape and for estimating the present recordingand playback position, and it is not too much to say that a transparentwindow is an indispensable feature in a magnetic tape cassette.

FIG. 2 illustrates an example of a method for forming a conventionaltransparent window. In this method, an opening 602 serving as the windowis formed at a predetermined position in an upper cassette half 601made, for example, of an ABS resin. A stepped portion 605 stepped in thedirection of the thickness of the cassette is provided around theopening 602. A plate 603 of a transparent synthetic resin having astepped portion 606 complementary in shape to the stepped portion 605 isfusingly bonded to the edge portion of the opening 602 to form thetransparent window.

The plate 603 is fusingly bonded to the edge portion of the opening 602usually by ultrasonic bonding. More specifically, a projection or fusionrib 604 is formed on the stepped portion 606 formed on the lower surfaceof the plate 603. The projection 604 is brought into contact with thestepped portion 605 defining the edge portion of the opening 602, andthen ultrasonic energy is applied to this contact region so that theprojection 604 is fused to bond together the plate 603 and the edgeportion of the opening 602.

In such ultrasonic bonding, as the area of contact between two parts tobe bonded together increases, the time required to effect fusion bondingis increased, lowering the operating efficiency.

For this reason, the projection 604 serving as the fusion rib isprovided. However, as a result of the provision of the projection 604,the height A used for positioning the fitting portion 607 of the plate603 is reduced by an amount corresponding to the height of theprojection 604. This makes it difficult to position the plate 603 withrespect to the opening 602 when the former is fitted in the latter. Inaddition, when ultrasonic energy is applied to the fusion portion toeffect ultrasonic bonding, the plate 603 is subjected to vibration. As aresult, the shoulder of the fitting portion 607 sometime rides on thestepped portion 605 damaging the plate 603.

Although it can be considered to thicken the plate 603 in order toovercome the above problems, this is not desirable because it lowers thetransparency of the window and increases the cost. In addition, sincethe plate 603 is subject to vibration upon application of ultrasonicenergy to the fusion portion during the ultrasonic bonding, it isdifficult to accurately determine the size of the opening 602. For thisreason, it has been necessary to make the size of the opening larger,taking the vibration of the plate 603 into account. As a result, uponassembly, there is created a gap between the fitting portion 607 and theedge of the opening 602. Further, when the magnetic tape cassette iscarried or when it is stored on a rack, the surface of the plate 603 issusceptible to damage such as by scratching, and the transparency of thewindow can thereby be lowered.

Thus, there is a problem in that the overall appearance of the magnetictape cassette can readily be marred.

Moreover, the invention relates to a magnetic tape cassette having aguide member for stabilizing the running of the magnetic tape in thecassette.

Magnetic tape cassettes for audio and video use are provided with guidemembers such as an immovable tape guide in sliding contact with themagnetic tape and guide roller rotatably engaged with the magnetic tapeto guide the running of the tape. These guide members are arranged incontact with either the backside (the base side) or the front side (themagnetic layer side) of the magnetic tape. Particularly, the rotatableguide roller is used mainly because its use avoids unnecessaryfrictional sliding contact with the magnetic tape.

As discussed above, such guide members are generally of a cylindricalshape, and some have a flange at its lower end or flanges at its upperand lower ends, respectively. Generally, the guide member is made of aplastics material having a relatively high wear resistance, such as aPOM resin. The magnetic tape is in sliding contact with the outerperiphery of the guide member, that is, the tape extends around theguide member through a certain angle, and therefore the guide memberconsiderably influences the running of the magnetic tape. Recently, arecording and playback device as well as a magnetic tape cassette hasbeen required to have a high performance to meet a high densityrecording and playback, and accordingly the guide member has beenrequired to have an improved performance. Particularly, in video tapecassettes of the type in which recording and playback are effecteddigitally, the problem of the tape running has become important.

A magnetic tape cassette having the above-mentioned guide member isdescribed, for example, in TELEVISION TECHNOLOGY, December 1986, page 45(see, in particular, FIG. 20 of this article).

The guide member is made of a POM resin as described above. One problemis that the use of a resin of a high wear resistance such as a POM resinincreases the cost of the cassette. Such a guide member of high wearresistance can be produced at a lower cost by molding a hollow or solidcylindrical body using a more inexpensive resin, and coating anultraviolet-curing coating onto the outer peripheral surface of thecylindrical body with which the magnetic tape is to be disposed insliding contact.

However, since the surface electrical resistance of a resin subjected toultraviolet-curing is very high, static electricity is liable to developwhen the magnetic tape is moved in sliding contact with the outersurface of the guide member. This causes a problem in that the magnetictape is then undesirably attracted to the surface of the guide memberbecause of the static electric charge, thus rendering the tape runningunstable.

SUMMARY OF THE INVENTION

An object of the invention is to overcome the above-discussed problemsand to provide a magnetic tape cassette in which the amount of wear ofthe cassette half due to the sliding movement of the slider issignificantly reduced, thereby achieving an excellent dust preventioneffect.

The above object of the present invention is achieved by a magnetic tapecassette wherein a magnetic tape wound around a pair of hubs issupported in a hollow interior of a cassette comprising upper and lowercassette halves in such a manner that the magnetic tape can run therein,part of the magnetic tape being pulled exteriorly of the cassettethrough an opening provided at a front side of the cassette andconstituting part of a path of travel of the magnetic tape, whereinthere is provided a slider slidingly movable along a bottom surface ofthe lower cassette half in forward and rearward directions with respectto the cassette so as to open and close a lower side of the opening, aplurality of ribs for reducing the coefficient of friction are formed onthe outer surface of the lower cassette half with which the slider isdisposed in aligning contact, the ribs extending in the direction ofsliding movement of the slider, and hard coatings for reducing wear dueto the sliding movement of the slider are formed on surfaces of theribs.

Objects of the invention are also achieved by a magnetic tape cassettewherein positioning holes are provided for positioning the cassette whenthe cassette is to be loaded into a recording and playback device, and amagnetic tape wound around a pair of hubs is supported within a cassettecase so that the magnetic tape can run so as to effect recording andplayback, wherein hard coatings for reducing wear due to slidingmovement are formed on inner peripheral surfaces of the positioningholes.

More specifically, hard coatings made, for example, of ultraviolet-curedresins are formed on the inner peripheral surfaces of the positioningholes. With this arrangement, even if the cassette case is made entirelyof a general-purpose having a low wear resistance such as an ABS resin,and even when the positioning pins of metal rub the inner peripheralsurfaces of the positioning holes, the wear of the inner peripheralsurfaces of the positioning holes is reduced because of the formation ofthe hard coatings of high wear resistance thereon.

A further object of the present invention is to provide a magnetic tapecassette storage case which is resistant to damage and which provides animproved dust prevention effect.

This object is achieved by forming a hard coating on a surface of astorage case, and particularly on a transparent or semi-transparentsurface thereof through which an index card or the like is visible, andalso by forming hard coatings on pivotal portions for a casing and a lidand those portions near the pivotal portions.

More specifically, the storage case itself is made of an AS resin, a PSresin or a PP resin, and the hard coatings are formed on those surfacesof the storage case susceptible to damage as well as those portionsliable to produce rubbed-off powder. Therefore, the hardness of thoseportions on which the hard coatings are formed is increased, and surfacedamage as well as the production of rubbed-off powder resulting from therubbing of the pivotal portions are eliminated.

Yet another object of the invention is to overcome the above problemsand to provide a magnetic tape cassette in which wear at the portions ofthe cassette case and the tape winding body in contact with each otherare prevented, and the cassette has good magnetic recordingcharacteristics and can be manufactured at a lower cost.

This object is achieved by a magnetic tape cassette wherein tape windingbodies on which a magnetic tape is wound are housed in a cassette casewherein a hard coating is formed on one or both contact portions of eachtape winding body and the cassette case, the tape winding bodycontacting part of the cassette case.

More specifically, hard coatings made, for example, of anultraviolet-curing resin, are formed on the surfaces of the abovecontact portions. With this construction, even if the cassette case ismade entirely of a general-purpose resin of a low wear resistance suchas an ASB resin, when the tape winding bodies rub the cassette case, thewear of the cassette case is reduced since the surfaces of the abovecontact portions are protected by the respective hard coating layers ofa high wear resistance.

Yet another object of the invention is to provide a magnetic tapecassette incorporating a pad for stabilizing the running of the magnetictape, which pad can be manufactured at a lower cost but which has anincreased wear resistance, thereby ensuring stable running of themagnetic tape.

This object is achieved by a magnetic tape cassette rotatably housing apair of hubs on which a magnetic tape is wound, wherein a resilient pad,which is held in sliding o contact with the magnetic tape and urges themagnetic tape so as to stabilize the running of the magnetic tape, has ahard coating of an ultraviolet-curing resin formed on a portion thereofwhich is in contact with the magnetic tape.

More specifically, the resilient pad comprises a plate-like base made ofan inexpensive synthetic resin such as a PET resin, and the hard coatingis formed on the portion of the pad disposed in contact with themagnetic tape, using the ultraviolet-curing resin. Thus, a resilient padhaving an excellent wear resistance is provided using inexpensivematerials, and the pad can be manufactured by a simple process.Therefore, the manufacturing cost of the pad can be reduced.

A still further object of the invention is to overcome the aboveproblems and to provide a magnetic tape cassette incorporating atransparent window which is resistant to damage and which can easily bemounted on the cassette.

This object is achieved by a magnetic tape cassette comprising upper andlower cassette halves defining a hollow cassette case within which amagnetic tape wound on a pair of hubs is mounted so that the magnetictape can run, the upper cassette half having a transparent window at anupper wall thereof, wherein the transparent window comprises atransparent synthetic resin plate sealing an opening formed through theupper wall of the upper cassette half, and the synthetic resin plate isbonded to an edge portion of the opening by an ultraviolet-cured resinformed therebetween.

More specifically, the curing of the ultraviolet-cured coating iscarried out by ultraviolet radiation. The invention has been made inview of the fact that the synthetic resin plate is transparent andtherefore allows ultraviolet to transmit therethrough. With thisconstruction, there is no need to form a fusion rib on the syntheticresin plate, and also there is no need to apply ultrasonic energythereto. Therefore, the positioning of the synthetic resin plate isfacilitated.

One more object of the invention is to provide a magnetic tape caseincorporating a guide member capable of preventing a static electriccharge caused by a sliding contact of the magnetic tape therewith and ofensuring stable running of the magnetic tape.

This object is achieved by a magnetic tape cassette incorporating aguide member disposed in sliding contact with a magnetic tape forstabilizing the running of the magnetic tape, wherein the guide membercomprises a hollow or solid cylindrical body molded of a syntheticresin, an antistatic ultraviolet-cured coating of a low electricalresistance, and a high-hardness ultraviolet-cured coating, both of whichcoatings are formed on an outer peripheral surface of the cylindricalbody in an intermingled manner in the form of stripes extendinggenerally along the axis of the cylindrical body.

The static charge produced as a result of the sliding contact betweenthe magnetic tape and the high-hardness ultraviolet-cured coating isdischarged through the antistatic ultraviolet-cured coating disposedadjacent the high-hardness ultraviolet-cured coating. Therefore, themagnetic tape will not be attracted to the guide member. Also, thehardness (wear resistance) of the guide member is increased, therebyensuring stable running of the magnetic tape over a prolonged period oftime.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an important portion of a tape recordershowing a loading operation of a magnetic tape cassette;

FIG. 2 is a fragmentary cross-sectional view of a conventional magnetictape cassette showing a transparent window construction;

FIG. 3 is a view showing the appearance of a magnetic tape cassette asviewed from a bottom side thereof;

FIG. 4 is a perspective view showing a lower cassette half and a slider;

FIG. 5 is a cross-sectional view of an important portion of a magnetictape cassette;

FIG. 6 is a partly broken away perspective view of the magnetic tapecassette of FIG. 5;

FIG. 7 is a fragmentary cross-sectional view showing a loading operationof a preferred embodiment of a magnetic tape cassette of the presentinvention;

FIG. 8 is a view showing the appearance of another preferred embodimentof a cassette storage case of the present invention showing the cassettestorage case and a magnetic tape cassette to be stored in the storagecase;

FIG. 9 is a cross-sectional view of an important portion of the storagecase showing a hard coating on a lid;

FIG. 10 is a cross-sectional view of an important portion of the storagecase showing hard coatings formed on a pivot pin and a hole;

FIGS. 11A-11C are cross-sectional views of important portions of thestorage case showing hard coatings formed on a projection and anengaging hole;

FIG. 12 is a cross-sectional view of an important portion a videomagnetic tape cassette according to a further embodiment of the presentinvention;

FIG. 13 is a perspective view of a portion of the video magnetic tapecassette of FIG. 12;

FIG. 14 is a cross-sectional view of an important portion of an audiomagnetic tape cassette according to another embodiment of the presentinvention;

FIG. 15 is a perspective view of a preferred embodiment of a resilientpad of the present invention;

FIG. 16 is a partly broken-away top plan view of a portion of a magnetictape cassette showing the manner of mounting of the resilient pad;

FIG. 17 is a perspective view of a relevant portion of the magnetic tapecassette showing the manner of mounting of the resilient pad;

FIG. 18 is a perspective view of another embodiment of a resilient padof the present invention;

FIG. 19 is an enlarged cross-sectional view of a portion of theresilient pad of FIG. 18;

FIG. 20 is a perspective view of a still another magnetic tape cassetteembodying the present invention;

FIG. 21 is a fragmentary cross-sectional view of the magnetic tapecassette;

FIG. 22 is a perspective view of a preferred embodiment of a tape guideof the present invention;

FIG. 23 is a developed view showing the arrangement of a high-hardnessultraviolet-cured coating and an antistatic ultraviolet-cured coating;

FIG. 24 is a plan view of a relevant portion of a video tape cassetteshowing a tape guide; and

FIG. 25 is a fragmentary perspective view showing the sliding contactportion between the tape guide and the magnetic tape.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferred embodiments of the present invention will now be described indetail with reference to the drawings.

FIG. 3 is a view showing the appearance of a magnetic tape cassette 1embodying the present invention, particularly, showing a bottom sidethereof.

When the magnetic tape cassette 1 is not in use, a guard panel 3attached to a front portion of an upper cassette half 2, that is, theloading side of the cassette relative to the DAT (not shown), is in itsclosed position, and a slider 5 which is reciprocally movable indirections of arrows A and B along the bottom surface of a lowercassette half 4 is lockingly held at the above front portion by a lockmechanism (not shown).

In this condition, a pair of reel shaft insertion holes 6a and 6b formedthrough the lower cassette half 4 are not disposed in alignment with therespective reel shaft insertion holes 7a and 7b formed through theslider 5. Therefore, the cassette halves 2 and 4, the guard panel 3, andthe slider 5 jointly provide a dust prevention assembly for a magnetictape (not shown) wound around a pair of hubs (not shown).

When the magnetic tape cassette 1 is loaded into a DAT, that is, in use,the slider 5 is caused to move in the direction of an arrow B to itsstop position where the reel shaft insertion holes 7a and 7b aredisposed in alignment with the reel shaft insertion holes 6a and 6b,respectively, so that a pair of reel shafts (not shown) are passedthrough these two pairs of aligned holes to drive the pair of hubs forrotation.

At this time, the guard panel 3 is rotated upwardly, that is, in thedirection of an arrow C, about pivot pins 8 passing through the upperhalf cassette 2 at opposite sides thereof. As a result, an opening ormouth portion 9 of the magnetic tape cassette 1 (FIG. 4) is opened, sothat the magnetic tape is exposed at the front side of the cassette andis pulled out by a recording/playback device for contact with a magnetichead.

Next, the sliding structure of the slider will be described withreference to FIGS. 4 and 5.

The lower cassette half 4 is of a box-like configuration defined by alower base 11, walls 12, 13 and 14 formed on three respective sides ofthe lower base 11 in a surrounding relation thereto, and a wall 16having a generally U shape when viewed from the top of the lowercassette half. The upper edges of the walls 12 and 14 are inclinedtoward each other, and these inclined surfaces 12a and 14a serve asguide portions for the slider 5.

The slider 5 is defined by a flat portion 21 and guide portions 22 and23. The guide portions 22 and 23 have inclined surfaces 22a and 23a,respectively, which are in sliding contact with the inclined surfaces12a and 14a, respectively.

As shown in FIGS. 3 and 5, two ribs 24 and 25 of a semi-circularcross-section are formed on the bottom surface of the lower cassettehalf 4. The ribs 24 and 25 are provided for the purpose of decreasingthe area of contact between the slider 5 and the bottom surface of thelower cassette half 4 when the slider is slidingly moved in thedirections of arrows A and B, thereby rendering this sliding movementsmooth and reducing the production of the above-mentioned rubbed-offpowder.

However, the provision of only the ribs 24 and 25 is not sufficient, andtherefore in this embodiment ultraviolet-cured coatings 24a and 25a areformed on the surfaces of the ribs 24 and 25, respectively. Theultraviolet-cured coatings 24a and 25a can be formed by applying to thesurfaces of the ribs 24 and 25 an ultraviolet-curing agent such as oneof the unsaturated polyester type, the unsaturated urethane-acrylatetype, the unsaturated epoxy-acrylate type, the unsaturatedpolyester-acrylate type or the like, and then applying ultraviolet tothe coated agent to effect surface curing.

As a result, the lower cassette half 4 as well as the upper halfcassette 2 can be made of an ABS resin or a PS resin, while the ribs 24and 25 have a high surface hardness and an increased wear resistance.Therefore, even if the slider 5, which is made of a POM resin, isslidingly moved repeatedly over the ribs 24 and 25 for a prolongedperiod of time, very little rubbing wear of the ribs will occur becauseof their increased wear resistance. In other words, rubbed-off powderwill hardly be produced, and therefore there is hardly any powder toadhere to the magnetic tape. Therefore, little or no signal dropout willoccur. Thus, almost perfect dust prevention measures are achieved.

In addition to the above-mentioned portions, the dust preventionmeasures achieved by the ultraviolet-cured coatings 24a and 25a can alsobe applied to those portions near the path of travel of the magnetictape, thereby further enhancing the dust prevention effect.

For example, the guard panel 3 is angularly movably mounted on the uppercassette half 2 by the pivot pins 8 each passing through a respectiveone of apertures 30 formed in the upper half cassette, as shown in FIG.6, and with this arrangement rubbed-off powder is liable to be producedsince the pivot pins 8 and the inner surfaces of the apertures 30 rubtogether. Moreover, the apertures 30 are disposed in the vicinity of themouth portion 9 and hence near the running magnetic tape.

Therefore, there is a great risk that the rubbed-off powder from theinner surfaces of the apertures 30 will adhere to the magnetic tape. Toprevent this, the above-mentioned ultraviolet-cured coating can beformed on the inner surface of each aperture 30. Thus, by formingultraviolet-cured coatings on those portions which are liable to producerubbed-off powder, the dust prevention effect can be markedly improved,thereby enhancing the reliability of the magnetic tape cassette.

Although the above embodiment relates to an audio magnetic tapecassette, the invention is, of course, applicable to video magnetic tapecassettes.

In the invention as described above, the plurality of ribs for slidingcontact with the slider are formed on the bottom surface of the lowercassette half of the magnetic tape cassette so as to reduce thecoefficient of friction, and the hard coatings cured by ultraviolet areformed on the surfaces of these ribs. As a result, the lower cassettehalf will not suffer rubbing damage by the slider when the latter isslidingly moved so that rubbed-off powder never adheres to the magnetictape. This enhances the dust prevention effect and maintains a goodsliding movement of the slider over a prolonged period of time.

Further, according to the present invention, the cassette case can bemade of a material which is inexpensive and can be easily molded, suchas an ABS resin and a PS resin. Therefore, there can be obtained amagnetic tape cassette of high performance having an excellent dustprevention effect, and which can be manufactured at a low cost.

FIG. 7 is a fragmentary cross-sectional view showing a loading operationof a magnetic tape cassette 220 of a second embodiment of the presentinvention.

The magnetic tape cassette 220 has two positioning holes 221a and 221bdisposed at a front portion thereof and opening in the direction of thethickness of the cassette. Ultraviolet-cured coatings 203 are formed onthe inner peripheral surfaces of the positioning holes 221a and 222a.

When the magnetic tape cassette 220 is loaded into a magnetic tapeloading portion 205 of a tape recorder body 201, the cassette isinserted into a bucket 202, and then the bucket 202 is angularly movedin the direction of an arrow B together with the magnetic tape cassette220, as is the case with a conventional cassette.

At this time, positioning pins 207a and 207b, formed on the magnetictape loading portion 205 in a projecting manner, are inserted into thepositioning holes 221a and 221b, respectively.

The positioning pins 207a and 207b are inserted into the respectivepositioning holes 221a and 221b in such a manner that the holes 221a and221b are disposed in inclined relation to the axes of the pins 207a and207b, respectively. Therefore, the positioning pins 207a and 207b areinserted through the positioning holes 221a and 221b, respectively, insuch a manner the pins 207a and 207b rub the inner peripheral surfacesof the holes 221a and 221b, respectively. After this inserting operationis completed, the positioning pins 207a and 207b are disposed coaxiallywith the positioning holes 221a and 221b, respectively.

In the present invention, however, the ultraviolet-cured coatings 203are formed on the inner peripheral surfaces of the positioning holes221a and 221b, respectively, and therefore the thus-coated innerperipheral surfaces are not easily worn. Accordingly, even when theseinner peripheral surfaces are rubbed by the positioning pins 207a and207b, they are hardly subjected to wear, and powder resulting from suchrubbing is hardly produced.

The ultraviolet-cured coatings 203 are formed by applying to the innerperipheral surfaces of the positioning holes 221a and 221b anultraviolet-curing agent such as one of the unsaturated polyester type,the unsaturated urethane-acrylate type, the unsaturated epoxy-acrylatetype and the unsaturated polyester-acrylate type, and then applyingultraviolet to the coated agent to effect the surface curing. Therefore,the cassette case can be molded, using conventionally-employed resin andmolding method, and then the ultraviolet-cured coatings 203 can beformed on the above-mentioned inner peripheral surfaces. Thus, thecassette can be easily manufactured.

Therefore, in the above embodiment, wear of the positioning holes can beprevented, and production of the powder resulting from the rubbing canbe reduced. Hence, there is provided a magnetic tape cassette which hasgood magnetic recording characteristics and which can be manufactured atlow cost.

Based on the principles of the present invention, the application of theultraviolet-cured coatings 203 is not limited to the positioning holes221a and 221b, and such coating can be applied to the capstan insertionholes 222, the openings 225 and 226. Further, the application of theinvention by which prevention of the rubbing-off of the cassettematerial through the use of ultraviolet-cured coatings is not limited toaudio magnetic tape cassettes as in the above embodiment, but can alsobe extensively applied to a video cassette, a floppy disc cartridge andthe like.

In the magnetic tape cassette according to this embodiment of thepresent invention, the hard coatings for reducing wear are formed on theinner peripheral surfaces of the positioning holes which serve toperform a positioning function when the cassette is loaded into therecording and playback device. With this arrangement, the deformation ofthe positioning holes as well as the production of the powder resultingfrom rubbing can be reduced. Therefore, such rubbed-off powder, whichcauses various troubles such as signal dropout due to the adhering ofsuch powder to the magnetic tape, is not produced, and therefore themagnetic recording characteristics of the magnetic tape cassette can beimproved.

Further, the cassette case of the magnetic tape cassette is made of amaterial which can be produced at low cost such as an ABS resin, and thecassette case is hardened at the necessary portions thereof. Therefore,the manufacturing cost can be greatly reduced as compared to a cassettemade entirely of a specially cured resin, and an inexpensive magnetictape cassette can be provided.

A third preferred embodiment of the present invention will now bedescribed in detail.

FIG. 8 is a perspective view showing a storage case 301 embodying theinvention and a magnetic tape cassette 320 to be stored in the storagecase 301.

The storage case 301 includes a lid 302 having a pocket 304 into whichthe magnetic tape cassette 320 is adapted to be inserted, and a casing305 having a pair of rotation prevention lugs 307 for insertion intorespective shaft insertion holes 322 of the magnetic tape cassette 320.Pivot pins 309 are formed on inner surfaces of right and left side wallsof the casing 305, and are fitted respectively in holes 310 formedthrough right and left side walls of the pocket 304. With thisarrangement, the casing 305 and lid 302 of the storage case 301 can beopened and closed with respect to each other in the manner of a door.

Projections 311, each having a semi-spherical end, are also formed onrespective inner surfaces of the right and left walls of the casing 305,and are adapted to be fitted in engaging holes 312 formed through theright and left walls of the pocket 304 when the lid and the casing 305are in the closed condition.

When the magnetic tape cassette 320 is to be stored in the storage case301, the magnetic tape cassette 320 is inserted into the pocket 304 in adirection indicated by an arrow, and then the lid 302 is angularly movedtoward the casing 305 to close the storage case.

As a result, the magnetic tape cassette 320 is interposed between a wall303 of the lid 302 and a wall 306 of the casing 305 in such a mannerthat a thickened portion 321 (i.e., the front portion) of the magnetictape cassette 320 having openings at one end thereof is received withinthe pocket 304, with the rotation prevention lugs 307 receivedrespectively in shaft insertion holes 322 of the magnetic tape cassette320.

In this stored condition (in which no index card is present), an index323 bonded to the surface of the magnetic tape cassette 320 can be seenthrough the wall 303. However, if the wall 303 is subjected to damagedue to rubbing or the like, the index 323 cannot be easily seen, whichis further undesirable from the viewpoint of appearance.

Therefore, in this embodiment of the present invention, anultraviolet-cured coating 303a is formed on an outer surface of the wall303 to harden the surface of the wall 303, as shown on an enlarged scalein FIG. 9. As a result, even if the lid 302 and the casing 305 are madeof an AS resin, a PS resin or a PP resin, which possess goodprocessability and are inexpensive, the wall 303, which is the easiestpart to damage, is rendered resistant to damage. Therefore, the index323 bonded to the magnetic tape cassette 320 remains clearly visible,and the appearance of the cassette will not be degraded. In the casewhere an index card (not shown) is provided internally of the lid 302,the index 323 is viewed through the wall 306. Therefore, in this case,an ultraviolet-cured coating 303a is similarly formed on the outersurface of the wall 306 as described above for the wall 303.

Also, as shown in FIG. 10, ultraviolet-cured coatings are formed on thepivotal portion constituted by the pivot pin 309 and hole 310 engagedwith each other. More specifically, the ultraviolet-cured coating 309ais formed on the surface of each pivot pin 309, and theultraviolet-cured coating 310a is formed on the inner surface of eachhole 310.

Although in FIG. 7, the pivot pin 309 does not extend through the hole310 for illustration purposes, the former extends through the latter inthe assembled condition so that the lid 302 and the casing 305 areangularly movable about the pivot pins 309 relative to each other in themanner of a door to open and close the storage case, as described abovewith reference to FIG. 8. Therefore, by virtue of the provision of theultraviolet-cured coatings 309a and 310a, the materials of the lid 302and the casing 305, such as an AS, PS or PP resin, will not rub togethereven when the pivot pin 309 is passed through the hole 310. Further, dueto the provision of the ultraviolet-cured coatings 309a and 310a, theirsurfaces which together are hardened so that the production ofrubbed-off powder of the resin constituting the storage case isprevented.

The engagement of the projection 311 with the engaging hole 312 iscarried out in the order shown in FIGS. 11A, 11B and 11C. These portionsare suitably subjected to surface hardening treatment to prevent dustgeneration. More specifically, as shown in these figures, anultraviolet-cured coating 311a is formed on the surface of eachprojection 311, and an ultraviolet-cured coating 312a is formed on theinner peripheral surface of each engaging hole 312. Further, anultraviolet-cured coating 313 is formed on that surface of each of theleft and right side plates 302a and 302b over which a respective one ofthe projections 311 slidingly moves when the storage case is opened andclosed. More specifically, concerning the side plate 302a, theultraviolet-cured coating 313 is formed on that surface thereofextending from a region where the projection 311a is brought intocontact with this side wall to a region where the hole 312 is provided.

Therefore, when the lid 302 and the casing 305 are to be closed relativeto each other, the projection 311 rides over the ultraviolet-curedcoating 313 as shown in FIGS. 11A and 11B. Then, the projection 311slidingly moves over the surface of the side wall 302a toward theengaging hole 312. At this time, since the ultraviolet-cured coatings311a and 313 are interposed between the projection 311 and the sideplate 302a, rubbed-off powder is hardly produced even if this slidingmovement is effected under a relatively great force.

On the other hand, when the lid 302 and the casing 305 are completelyclosed relative to each other, the projection 311 is fully fitted in theengaging hole 312 as shown in FIG. 11C. At this time, the projection 311is press-fitted in the engaging hole 312 under the resilience of theside plate of the casing 305. As a result, the lid 302 and the casing305 are held together in a unitary fashion. The holding force will notbe released unless an external force such as a force applied by thefingers is exerted on the storage case, thereby enhancing the protectivefunction of the storage case.

As described above, the ultraviolet-cured coating 311a is formed on thedistal end portion of each projection 311, and the ultraviolet-curedcoating 312a is formed on the inner peripheral surface of each engaginghole 312. Therefore, neither the projection 311 nor the engaging hole312 is worn, thus producing no rubbed-off powder when the former isfitted in the latter. The pivot pins 309, through-holes 310, projections311, and engaging holes 312 are disposed near the openings of themagnetic tape cassette 320 when the magnetic tape cassette is insertedinto the pocket 304. Therefore, if the production of such rubbed-offpowder is not prevented, the rubbed-off powder would adhere to themagnetic tape. In this embodiment of the present invention, however,such rubbed-off powder is not produced, and therefore one of thefundamental reasons for the dust generation is eliminated. Theabove-mentioned ultraviolet-cured coatings can be formed by applying aultraviolet-curing agent to those portions on which the coatings are tobe formed, and then subjecting the thus-coated agent to ultravioletradiation. In this embodiment, the lid 302 and the casing 305 can bothbe transparent so that the direction of radiation of the ultraviolet isnot limited, which advantageously simplifies the manufacturing process.

Further, the above ultraviolet-cured coating may be applied to otherportions subjected to frequent abrasion, such as the rotation preventinglugs 307.

Further, instead of applying the ultraviolet-cured coating to one of thesurfaces of the walls 303 and 306, this coating may be applied to theopposite surfaces of each of these walls. In this case, the problem ofappearance is fully overcome, and the index 323 can be clearly seen fromeither side as desired. Further, the hard coating may be formed on thewhole of the storage case 301.

In the above embodiment, although the pivot pins 309 and the projections311 are formed on the casing 305 while the holes 310 and the engagingholes 312 are formed through the lid 302, the holes 310 and the engagingholes 312 may be formed through the casing 305 while the pivot pins 309and the projections 311 are formed on the lid 302. In either case, theobjects of the present invention can be fully achieved by providing theultraviolet-cured coatings in the manner mentioned above.

Although the above embodiment has been described with reference to astorage case for an audio magnetic tape cassette, the invention is notrestricted to such an embodiment, and can be extensively applied, forexample, to a video magnetic tape cassette storage case composed of theabove-mentioned plastics resins and also to a storage case for 3.5 -inchfloppy disks.

As described above, according to the present invention, by forming hardcoatings on the surface of the wall of the casing of the magnetic tapecassette storage case and the surface of the wall of the lid, the wearresistance of these wall surfaces is enhanced, and the appearance of thecassette will not be marred even if the storage case is made of aninexpensive material and used over a prolonged period of time.

Further, by forming the hard coatings on the support portions forangularly movably supporting the casing and lid constituting the storagecase and also on the retaining portions for retaining the casing and thelid relative to each other, the wear resistance of these supportportions and retaining portions is enhanced, and rubbed-off powder isnot produced to thereby improve the dust prevention effect of thestorage case.

Another preferred embodiment of the present invention will now bedescribed in detail with reference to the drawings.

FIG. 12 is a cross-sectional view of an important portion of a videomagnetic tape cassette.

The magnetic tape cassette 401 includes upper and lower cassette halves402 and 403, each of one-piece molded construction made of an ABS resin.A pair of flanged tape reels 405 on which a magnetic tape T is wound arehoused in the space defined by the upper and lower cassette halves.

A leaf spring 404 is secured to an inner surface of the upper cassetteball 402 at a central portion thereof. The distal end 404a of the leafspring 404 urges a pivot 407 inwardly of the cassette which pivot isformed on an upper surface of the tape reel 405 and disposed at the axisthereof.

An opening 408 is formed through a base wall of the lower cassette half403 for inserting a drive shaft (not shown) into a reel hub 406therethrough to drive each tape reel 405.

Ultraviolet-cured coatings 411 are formed on the outer peripheral edgesof flanges 409 and 410 of the tape reel 405, an inner surface of theside wall of the cassette case, the pivot 407 and the inner surface ofthe lower cassette half defining the inner surface of the bottom of thecassette case.

Due to vibration or other movement developing, for example, duringtransportation of the magnetic tape cassette 401, the outer peripheraledges of the flanges 409 and 410 of the tape reel 405 and the side wallof the cassette case slidingly contact each other and rub together, andthe outer surface of the lower flange 410 and the above inner surface ofthe lower cassette half 403 slidingly contact each other and rubtogether.

According to the present invention, however, because theultraviolet-cured coating 411 is formed on at least one of each matingcontact surfaces, wear resistance is imparted thereto.

The pivot 407 always slidingly contacts the leaf spring 404 during therotation of the tape reel 405 so that rubbed-off powder is liable to beproduced. To prevent this, the ultraviolet-cured coating 411 is alsoformed on the surface of the pivot 407 so as to prevent the productionof such rubbed-off powder.

In a video magnetic tape cassette, a locking pawl (not shown) is adaptedto be lockingly engaged with a continuous serration 416 formed on theouter periphery of the lower flange 410 to prevent the tape reel 405from inadvertent rotation when the cassette is not in use. When thelocking pawl is moved into and out of locking engagement with theserration, rubbed-off powder tends to be produced. The formation of theabove-mentioned ultraviolet-cured coating on one or both of theserration 416 and the locking pawl will prevent the above dropoutproblem more positively.

The upper flange 409 is usually made of a transparent resin so that theremainder of the magnetic tape can be viewed from the outside of thecassette through a transparent window formed at the upper cassette half402. Therefore, if the surface of the upper flange 409 is subjected todamage due to contact with the upper cassette half 402 or the magnetictape T, the visibility through the upper flange is affected. By formingultraviolet-cured coatings 411 on the opposite sides of the upper flange409, the surfaces of the upper flange 409 is protected from damage,which is also desirable from the viewpoint of the appearance.

An audio magnetic tape cassette according to another embodiment of thepresent invention will now be described in detail with reference to FIG.14.

The audio magnetic tape cassette 412 includes upper and lower cassettehalves 413 and 414, each of a one-piece molded construction made of anABS resin. A pair of hubs 415 on which a magnetic tape T is wound arerotatably mounted through friction sheets 416 in a spaced defined by theupper and lower cassette halves.

More specifically, each of the annular hubs 415 is rotatably supportedby spool support walls 417 and 418 of a circular cross-section formedrespectively on the upper and lower cassette halves 413 and 414.

The magnetic tape T is wound around each reel hub 415. The reel hub 415is not provided with flanges, and instead the pair of upper and lowerfriction sheets 416 prevent the magnetic tape T from being displaced inthe vertical direction.

Usually, the friction sheets 416 are fixedly mounted on the respectiveopposed inner surfaces of the upper and lower cassette halves 413 and414. An ultraviolet-cured coating 411 is formed on an outer surface ofeach of the spool support walls 417 and 418.

When the magnetic tape T runs, the outer surfaces of the spool supportwalls 417 and 418 slidingly contact the upper and lower portions of theinner peripheral surface of the reel hub 415.

According to the present invention, the outer surfaces of the spoolsupport walls 417 and 418 are formed with the ultraviolet-cured coatings411 and therefore are resistant to wear.

The ultraviolet-cured coatings 411 on the above contact portions areformed by coating onto these contact portions an ultraviolet-curingagent, such as one of the unsaturated polyester type, the unsaturatedurethane-acrylate type, the unsaturated epoxy-acrylate type, theunsaturated polyester-acrylate type or the like, and then curing thecoated agent by application of ultraviolet to effect surface hardening.Therefore, the upper and lower cassette halves can be molded using theconventional resin material and the conventional method, and then theultraviolet-cured coating is formed on each of the above contactportions. Therefore, the manufacturing process is easy to implement.

In the above embodiments, the contact portions are prevented from wearto reduce the production of rubbed-off powder. Therefore, there isprovided a magnetic tape cassette which has good magnetic recordingcharacteristics and which can be manufactured at a low cost.

According to the principles of the present invention, the portions onwhich the ultraviolet-cured coatings 411 are to be formed are notlimited to the above contact portions, and this coating can be appliedto other various contact portions. Further, the present invention is notrestricted to the above embodiments and can be extensively applied to adigital audio cassette, a 8-mm video cassette and the like.

In the magnetic tape cassette according to the above embodiments of thepresent invention, a hard coating for reducing wear is formed on one orboth of the contact portions of each tape winding body having themagnetic tape wound therearound, the cassette case housing the tapewinding body, and the tape winding body contacting part of the cassettecase. With this arrangement, deformation of the contact portions and theproduction of rubbed-off powder are reduced. Thus, rubbed-off powder,which would otherwise adhere to the magnetic tape to cause variousproblems such as signal dropout, is not produced, thereby improving themagnetic recording characteristics of the magnetic tape cassette.

The cassette case of the magnetic tape cassette is made of a low-costresin such as an ABS resin, and only necessary portions are hardened.Therefore, the manufacturing cost can be very much lower than that of acassette made entirely of a special hard resin, and there can beprovided a magnetic tape cassette at a lower cost.

Other preferred embodiments of the present invention will now bedescribed with reference to the drawings.

FIG. 15 is a perspective view of a resilient pad of the presentinvention used in a magnetic tape cassette.

The resilient pad 501 is a one-piece plate-like base 502 molded of a PETresin in the form of a rectangular plate, and an ultraviolet-curedcoating 503 is formed on one side of the base at a front end portionthereof.

An opening 504 is formed through the base 502 at a central portionthereof so that the resilient pad 504 has a desired resiliency as awhole. Further, an adhesive layer 505 for attaching the resilient pad501 to the magnetic tape cassette is formed on the other side of thebase 502 at a proximal end portion thereof, which other side is oppositeto the side on which the ultraviolet-cured coating 503 is formed.

As shown in FIGS. 16 and 17, the resilient pad 501 of the aboveconstruction is mounted on the magnetic tape cassette 511 in aconventional manner.

In the magnetic tape cassette 511, a magnetic tape 12 fed from a reel516 runs through a guide pole 515 and a tape guide 514.

The tape guide 514 is cylindrical and is made of metal or a syntheticresin, the tape guide being rotatably fitted on a support pin of metalmounted on the magnetic tape cassette 511. The outer peripheral surfaceof each of the tape guide 514 and the guide pole 515 is smooth so thatit will not damage the magnetic tape 512. A rotatable roller may beloosely fitted on the guide pole 515.

The pad 501 is adhesively bonded to an inner side of a wall 513 of themagnetic tape cassette 511 disposed at a front portion of the cassette.The resilient pad 501 is designed so that, in this condition, theultraviolet-cured coating 503 is urged against the outer periphery ofthe guide pole 515 through the magnetic tape so that the resilient pad501 is curved or deformed in its longitudinal direction as shown in thedrawings. The elastic force produced by this deformation urges themagnetic tape 512 against the guide pole 515.

Therefore, when the magnetic tape 512 is to run in a direction of anarrow at a region close to a front opening of the magnetic tape cassette511, the magnetic tape 512 runs under a desired tension.

Since the resilient pad 501 always urges the magnetic tape 512 againstthe outer periphery of the guide pole 515, the magnetic tape 512 isalways held in sliding contact with the contact portion of the resilientpad 501.

In the above embodiment of the present invention, the ultraviolet-curedcoating 503 is formed on that contact portion so that the surface cannoteasily be worn. This coating is formed by coating an ultraviolet-curingagent such as one of the unsaturated polyester type, the unsaturatedurethane-acrylate type, the unsaturated epoxy-acrylate type or theunsaturated polyester-acrylate type, and then curing the coated agent byultraviolet radiation to provide a hardened surface.

Thus, the base 502 is made of an inexpensive PET resin, and theabove-mentioned hard coating can be formed at a low cost. Therefore, thecost of the resilient pad 501 and hence the overall cost of the magnetictape cassette 511 can be reduced.

Another embodiment of the invention will now be described with referenceto FIGS. 18 and 19.

Features of this embodiment reside in the shape of the ultraviolet-curedcoating and a method of forming it.

More specifically, a base 502, an opening 504 and an adhesive layer 505of a resilient pad 521 are the same as those described above. However,since an ultraviolet-cured coating 522 is formed by dipping, theultraviolet-cured coating 522 is formed on the opposite sides of thebase 502 as shown in FIG. 19 which is a longitudinal cross-sectionalview.

With this construction of the ultraviolet-cured coating 522, the frontend portion of the base 502 is entirely covered by the ultraviolet-curedcoating 522, and therefore the front edge of the base 502 is notexposed.

Hence, the magnetic tape 512 will never be damaged by this front edge,and the reliability of the magnetic tape cassette 511 is therebyenhanced.

In the magnetic tape cassette according to these embodiments, thepresent invention, the hard coating of the ultraviolet-cured resin forreducing wear is formed on the contact portion of the resilient pad heldin sliding contact while urging the magnetic tape so as to stabilize therunning of the magnetic tape, thereby reducing the wear of the resilientpad. Therefore, the base of the resilient pad can be molded of aninexpensive PET resin or the like, and the hard coating is formed onlyon the above contact portion by a simple process. As a result, the costof this resilient pad can be very much lower than that of a pad madeentirely of a special wear-resistant resin, and this pad ensures stablerunning of the magnetic tape. Therefore, there can be provided aninexpensive magnetic tape cassette.

FIG. 20 is a perspective view of another magnetic tape cassette, showingits general configuration. FIG. 21 is a fragmentary cross-sectionalview, showing a transparent window 615 of the magnetic tape cassette.

The magnetic tape cassette 611, which is used for a DAT (digital audiotape recorder), has a pair of upper and lower cassette halves 612 and613, and a magnetic tape (not shown) wound on a pair of tape reels (notshown) is mounted within a space defined by these cassette halves sothat the magnetic tape can run.

A pair of transparent windows 614 and 615 are provided at a flat portionof the upper cassette half 612 for the purpose of viewing the pair oftape reels and the magnetic tape.

A guard panel 620 is pivotally mounted by pivot pins 617a on a frontportion of the magnetic tape cassette 611 so as to be opened and closed.When the magnetic tape cassette 611 is not in use, the guard panel 620is in its closed position, as shown in the drawings, to thereby protectthe magnetic tape. This guard panel is opened when the cassette isloaded into the DAT, whereupon the magnetic tape is pulled by arecording and playback device exposed at a front portion of the DAT soas to contact a magnetic head.

In the magnetic tape cassette 611 of the above construction, thetransparent windows 614 and 615 are constructed as described below. Thetransparent windows 614 and 615 are of the same construction, andtherefore only one of them, namely, the transparent window 615, will nowbe described with reference to FIG. 21.

The transparent window 615 includes a transparent synthetic resin plate617 covering an opening 616 formed through the upper cassette half 612molded of a synthetic resin.

The shape and size of the opening 616 are determined taking intoconsideration the position of mounting of the tape reels and from aviewpoint of design. A stepped portion 618 is formed on and extendsalong the edge portion of the opening 616. The edge portion of thetransparent synthetic resin plate 617 is placed on the stepped portion618 through an ultraviolet-cured resin 619.

The ultraviolet-cured resin 619 is covered by the transparent syntheticresin plate 617 so that light can be transmitted to theultraviolet-cured resin through the plate 617. As a result, ultravioletlight is applied to the ultraviolet-curing resin 619 in the direction ofan arrow X when curing the resin 619.

The ultraviolet-curing resin 619 is cured in this manner. Theultraviolet-curing resin 619 has a bonding function and therefore servesto bond the edge portion of the transparent synthetic resin plate 617 tothe stepped portion 618 when the ultraviolet-curing resin 619 is cured.

The transparent windows 614 and 615 are assembled in the above-mentionedbonding steps. In the present invention, a projection serving in as afusion rib used in the conventional ultrasonic bonding is not needed. Inaddition, after proper positioning operation is effected, the syntheticresin plate 617 can be bonded by fusion without further moving it.Therefore, the synthetic resin plate 617 will not be displaced out ofposition and can be easily mounted.

As the ultraviolet-curing resin, there can be used an ultraviolet-curingresin of the unsaturated polyester type, the unsaturatedurethane-acrylate type, the unsaturated epoxy-acrylate type, theunsaturated epoxy-acrylate type, the unsaturated polyester-acrylate typeor the like.

The synthetic resin plate 617 can be made of any resin so long as theresin has light transmitting properties.

In another embodiment, a transparent ultraviolet-curing resin may becoated onto the upper surface of the synthetic resin plate 617, in whichcase this ultraviolet-curing resin on the upper surface can be curedsimultaneously with the curing of the ultraviolet-curing resin 619,thereby forming a hard coating on the above upper surface to protectagainst damage.

In this case, the fusion bonding of the transparent windows 614 and 615is carried out simultaneously with the surface hardening treatment ofthe transparent windows 614 and 615. This prevents the transparentwindows 614 and 615 from being subjected to damage in the course oflong-term use and therefore prevents its appearance from being marred.

In the above embodiment, the ultraviolet-curing resin 619 is appliedbetween the stepped portion 618 and the transparent synthetic resinplate 617. Instead of this arrangement, the ultraviolet-curing resin 619may be applied to an area of contact between the vertical edge surfaceof the opening 616 and the vertical edge surface of the synthetic resinplate 617, and then cured by application of ultraviolet light to bondthese two surfaces together.

The application of the present invention is not limited to DAT magnetictape cassettes, and the invention can be suitably applied to videomagnetic tape cassettes and other magnetic tape cassettes. Someconventional audio magnetic tape cassettes have upper and lower cassettehalves made of a transparent synthetic resin and fastened together byscrews. According to the present invention, such a construction can bemodified in such a manner that ultraviolet-curing resin is applied to anarea of contact between the upper and lower cassette halves to bond themtogether by application of ultraviolet. This obviates the need for theuse of the screws and a screw fastening operation, and therefore thecost can be greatly reduced.

As described above, after the ultraviolet-curing resin is coated on thebonding surface, this resin is cured by application of ultravioletlight. This facilitates the bonding operation on the assembly line tothereby improve the automation of the manufacturing process. Therefore,the magnetic tape cassette can be manufactured at a lower cost.

In the magnetic tape cassette according to the present invention, thesynthetic resin plate constituting the transparent window of themagnetic tape cassette is bonded to the edge portion of the opening ofthe upper cassette half through the ultraviolet-curing resin appliedbetween the synthetic resin plate and the edge portion of the opening.Therefore, there is no need to provide a fusion rib, which has beenrequired for the conventional ultrasonic bonding, and the shapes andconstructions of those portions to be bonded can be simplified. Inaddition, the ultraviolet-curing resin can be suitably cured byapplication of ultraviolet, which facilitates the bonding operation andimproves the easy of assembly of the magnetic tape cassette.

Further, when ultraviolet-curing resin is coated on the outer surface ofthe synthetic resin plate and then is cured, the transparent syntheticresin plate cannot easily be damaged. Therefore, there can be provided amagnetic tape cassette which is less costly and has an appearance whichcannot be easily marred.

Still further preferred embodiments of the invention will now bedescribed with reference to the drawings.

FIG. 22 is a perspective view of the tape guide used in a video tapecassette. FIG. 23 is a developed view of a surface of the tape guideshowing the arrangement of a high-hardness ultraviolet-cured resin andan antistatic ultraviolet-cured resin for illustration purposes.

The tape guide 701 of one-piece cylindrical shape is molded of an ABSresin which is relatively inexpensive and has a good moldability. Asshown in FIGS. 22 and 23, the high-hardness ultraviolet-cured resin andthe antistatic ultraviolet-cured resin are formed on an outer peripheralsurface 702 of the tape guide 701 in the form of stripes extending alongthe axis of the tape guide. More specifically, an antistaticultraviolet-curing resin is coated in the form of comb teeth and then iscured by application of ultraviolet light to form the antistaticultraviolet-cured coating 703. The high-hardness ultraviolet-curedcoatings 704 made of a high-hardness ultraviolet-curing resin arediscretely formed alternately with the antistatic ultraviolet-curedcoating 703 in the circumferential direction of the tape guide. Each ofthe high-hardness ultraviolet-cured coatings 704 is formed by coatingthe high-hardness ultraviolet-curing resin on the outer peripheralsurface 702 of the tape guide 701 in the shape of a rectangle and thencuring it by application of ultraviolet light.

There is no need to apply ultraviolet radiation twice, and this can becarried out at a time after the high-hardness ultraviolet-curing resinand the antistatic ultraviolet-curing resin are both coated.

The electrical resistivity of the antistatic ultraviolet-cured coating703 is determined to be not more than 1×10¹¹ Ω/cm, and the high-hardnessultraviolet-cured coatings 704 are determined to have a hardness, forexample, corresponding to a pencil hardness of not less than 5 H.

Examples of the high-hardness ultraviolet-curing resin include polyolacrylate resins made from compounds such as 1,6-hexane diol diacrylate,neopentyl glycol diacrylate, trimethylolpropane triacrylate,pentaerythritol triacrylate and pentaerythritol tetramethacrylate,polyester acrylate resins made from compounds such as α,ω-tetraacrylbis-trimethylolpropane tetrahydrophthalate and α,ω-dimethacrylbis-diethylene glycol phthalate, a urethane acrylate resin such as acompound obtained by reacting 2 -hydroxyethyl acrylate (HEA) with atolylene diisocyanate or isophorone diisocyanate and a compound obtainedby reacting hexane diol, isophorone diisocyanate and HEA, epoxy acrylateresins made from compounds such as diacrylate of bisphenol A diglycidylether and trimethylolpropane polyglycidyl ether polyacrylate, and otherincluding spiroglycol diglycidyl either diacrylate, silicone acrylateand trisacrylyl oxyethylene isocyanurate.

With respect to the antistatic ultraviolet-cured resin, its electricalresistivity can be adjusted to the above-mentioned value byincorporating an electrically conductive material, such as carbonparticles and fibers, into the above-mentioned polyfunctional acrylates.

The tape guide 701 is used in a video tape cassette in a manner shown inFIGS. 24 and 25.

The overall construction of the video tape cassette is described inprior publications, and therefore in this embodiment only a relevantportion thereof where the tape guide 701 used will be described.

A pair of tape reels 713 are rotatably mounted on a case 712 of thevideo tape cassette 711. At the time of a recording and playback, themagnetic tape 714 wound around one of the tape reels 713 (for example,the supply reel) runs in contact with a magnetic head (not shown)disposed exteriorly of the cassette case in such a manner that themagnetic tape is urged sliding contact with the outer peripheral surface702 of the tape guide 701.

With respect to the sliding contact between the magnetic tape 714 andthe tape guide 701, the magnetic tape runs in such a manner that itslidingly contacts the high-hardness ultraviolet-cured coating 704 andthe antistatic ultraviolet-cured coating 703 alternately.

Therefore, even if the magnetic tape is electrically charged when itslidingly moves over the high-hardness ultraviolet-cured coating 704,the magnetic tape is discharged when it is brought into sliding contactwith the subsequent antistatic ultraviolet-cured coating 703 having agood electrical conductivity.

Since the spaced portions of the antistatic ultraviolet-cured coating703 are connected together by its proximal portion (i.e., the upperportion in FIG. 22) in the form of a comb, the above discharge ispositively carried out. This prevents undesirable problems such as anunstable running of the magnetic tape caused by attraction to the outersurface 702 of the tape guide 701 due to the static electric charges.

Further, since the high-hardness ultraviolet-cured coatings 704 arearranged alternately with the antistatic coating and spaced at apredetermined interval, the outer peripheral surface 702 of the tapeguide 701 has an increased wear resistance, and therefore the tape guidecan be used over a prolonged period of time. Further, the increased wearresistance reduces the amount of rubbing-off of the outer peripheralsurface 702, and therefore rubbed-off powder is not produced. Thus, thisalso constitutes dust prevention measures.

Therefore, the video tape cassette to which the present invention isapplied can be manufactured at lower costs and is more reliable in taperunning performance and the like.

Although the above embodiment of the present invention has beendescribed, the present invention is not to be restricted to suchembodiment and various modifications can be made.

For example, depending on whether priority is given to the wearresistance or the antistatic property, the ratio of area of thehigh-hardness ultraviolet-cured coatings 704 to the antistaticultraviolet-cured coating 703 can be suitably changed.

Also, in the above embodiment, the high-hardness ultraviolet-curedcoatings and the antistatic ultraviolet-cured coating are alternatelyarranged in the circumferential direction of the tape guide 701 in theform of stripes extending parallel to the axis the tape guide. However,instead of this arrangement, for example, they can be arranged ininclined relation to the axis of the tape guide or can be arrangedspirally. With such an inclined arrangement, the high-hardnessultraviolet-cured coating 704 and the antistatic ultraviolet-curedcoating 703 can contact the magnetic tape 714 across the tape at thesame time even if the diameter of the tape guide 701 as well as theangle of extension of the magnetic tape 714 around the tape guide issmall. This positively achieves both of the antistatic effect and thewear resistance effect.

Further, the present invention is not restricted to the hollow or solidcylindrical member as described in the above embodiment, and can also beextensively applied to other guide members used in an audio tapecassette, a tape cassette for DAT and a tape cassette for an 8 mm video.

In the present invention, there is used the guide member which includesa body of a synthetic resin having a desired shape, for example, in theform of a hollow or solid cylinder, and the antistatic ultraviolet-curedcoating of a low electrical resistance and the high-hardnessultraviolet-cured coating for increasing a wear resistance, both ofwhich coatings are alternately formed on the outer peripheral surface ofthe cylindrical body in the form of stripes. Therefore, the guide membercan simultaneously overcome two contradictory problems, that is, theprevention of static charges and the improvement of wear resistance, andtherefore ensures stable running of the magnetic tape. Thus, in themagnetic tape cassette incorporating the above guide member, theattraction of the magnetic tape to the guide member due to the staticcharges will not occur, thereby stabilizing the tape running andenhancing the wear resistance. Thus, not only is the tape runningstabilized, but also the production of rubbed-off powder of the guidemember is restrained, thereby enhancing the reliability of the magnetictape cassette.

What is claimed is:
 1. In a magnetic tape cassette incorporating a guidemember disposed in sliding contact with a magnetic tape for stabilizingthe running of the magnetic tape, the improvement wherein said guidemember comprises a cylindrical body molded of a synthetic resin, anantistatic ultraviolet-cured coating having a low electrical resistanceof no more than 1×10¹¹ ohms/cm, and a high-hardness ultraviolet-curedcoating having a pencil hardness of at least 5 H, said high-hardnessultraviolet-cured coating having a pencil hardness of at least 5 H beingformed alternatively with the antistatic ultraviolet-cured coatinghaving a low electrical resistance of no more than 1×10¹¹ ohms/cm on anouter peripheral surface of the cylindrical body in the form of stripesextending generally along the axis of the cylindrical body, arranged inan inclined relation to the axis of the cylindrical body, or arrangedspirally.
 2. The magnetic tape cassette of claim 1, wherein saidhigh-hardness ultra-violet-cured coating is made of a material selectedfrom the group consisting of polyol acrylate resins, polyester acrylateresins, urethane acrylate reins and epoxy acrylate resins.
 3. Themagnetic tape cassette of claim 2, wherein the polyol acrylate resinsare selected from the group consisting of compounds made from 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, trimethylolpropanetriacrylate, pentaerythritol triacrylate and pentaerythritoltetramethacrylate.
 4. The magnetic tape cassette of claim 2, wherein thepolyester acrylate resins are selected from the group consisting ofcompounds made from α,ω-tetraacryl bis-trimethylolpropanetetrahydrophthalate and α,ω-dimethacryl bis-diethylene glycol phthalate.5. The magnetic tape cassette of claim 2, wherein the urethane acrylateresins are selected from the group consisting of compounds obtained byreacting 2-hydroxyethyl acrylate with a tolylene diisocyanate orisophorone diisocyanate and a compound obtained by reacting hexane diol,isophorone diisocyanate and 2-hydroxyethyl acrylate.
 6. The magnetictape cassette of claim 2, wherein the epoxy acrylate resins are selectedfrom the group consisting of compounds made from diacrylate of bisphenolA diglycidyl ether and trimethylolpropane polyglycidyl etherpolyacrylate, and spiroglycol diglycidyl ether diacrylate, siliconeacrylate and trisacrylyl oxyethylene isocyanurate.